This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Much has been said about the benefits of exercise to health. With our aging population, we are particularly interested in studying the relationship between physical activity and cognitive abilities (e.g. learning and memory) in the elderly populations. Currently, a number of studies on this relationship can be found in the literature, with some evidence suggesting that exercise provides benefits in protecting cognitive decline in old age. However, this conclusion remains unclear as a number of studies failed to show this relationship. Other studies involving older men suggested that low testosterone level is related to cognitive decline and Alzheimer's disease. Here, we propose a study to collect data on the amount of physical activity, memory performance, and testosterone levels in 30 healthy men between the age of 65 to 85. Participants will be recruited through advertisement at fitness centers, senior homes, as well as in newspapers. We aim to recruit 15 men with high activity (men who regularly exercise at least 3 times a week) and 15 men with low activity (men who exercise less than 2 times a week). The study period for each participant will be 2 weeks. Participants will wear a small activity monitor on their wrist and keep an activity diary through 2 weeks. At the end of the 2-week period, activity data (both measured and self-reported) will be collected. In addition, they will complete two memory tasks and have a blood draw for testosterone level measurement at their last visit at the end of the 2-week study period. The data collected in this pilot study will be analyzed to see if there is a relationship between the amount of physical exercise, memory performance and testosterone level in older men. The outcome of this study will provide useful research information, at the same time carry important public health implications.